Boiler with control to prevent overheating



Sept. 1, 1953 E. B. TIDD Filed April :50, 1952 4 Sheets-Sheet 1 r A/ f" 11 1 v 1 3'4- I 1 I i 44 r "7 r Sept. 1, 1953 E. B. TIDD A 2,650,576

- BOILER WITH CONTROL TO PREVENT OVERHEA'IING Filed April 30, 1952 4 Sheets-Sheet 2 wlrlrlll f' lm I A ll/lunar, mi 3a 23 '10, mg,

[dwzn E P 1, 1953 E. B, 'l 'lDD 2,650,576

BOILER WITH CONTROL TO PREVENT OVERHEATING Filed April 30, 1952 4 Sheets-Sheet 3 w N w "w v l IfiJenfor.

. EJwinB-Y'J'Hd! Sept. 1,. 1953 E. a. TIDD BOILER WITH CONTROL TO PREVENT OVERHEATING Filed April 30, 1952 4 Sheets-Sheet 4 can. WITH! .1-- Ta 501L217 Patented Sept. 1, 1953 BOILER WITH CONTROL TO PREVENT OVERHEATIN G Edwin B. Tidd, Mount Prospect, 11]., assignor to Bell & Gossett Company, Morton Grove, 111., a

corporation of Illinois Application April 30, 1952, Serial No. 285,141

20 Claims. 1

My invention relates to heating systems and is concerned primarily with an arrangement for automatically preventing overheating of the boiler.

In heating systems of the hot water type, overheating of the boiler may result from failure of the electrically operated controls to shut down the gas or oil burner when the boiler Water attains its maximum, safe working temperature, or in the case of a stoker or hand fired boiler, overheating may be caused by the fact that suificient fuel has been fed to the firebox to sustain continued heating of'the boiler after the hot Water circulating pump has, stopped. Under either of the above conditions, heating of the boiler continues and if the system is equipped with flow control valves which close when the circulating pump stops, the situation soon becomes critical because the valves confine the boiler Water and prevent its flow through the system where the heat could be dissipated.

As the temperature of the boiler water rises, the boiler pressure increases and where, as is usual in systems of this character, a pressure relief valve is associated with the boiler, this valve relieves the boiler pressure at the setting of the valve, ordinarily thirty pounds gage, although, as a matter of fact, such valves begin to open at about twenty-eight pounds which is evidenced by a slight drip at the valve. These valves alone, however, cannot be relied upon to protect the broiler against a high water temperature.

Overheating presents a series operating and economic problem in numerous localities because where the service water is indirectly heated by the boiler water to a temperature in excess of 140 R, deposits of lime are formed rapidly in the coils or tubes of the heater, thus reducing the rate or" heat exchange and lowering the temperature of the water available at the service outlets. This liming condition is continuously aggravated by recurrent periods of overheating.

It is therefore one object of my invention to provide means for automatically preventing overheating of a hot water boiler by utilizing the cold water supply as a cooling agent and permitting the cold water to flow in heat exchanging relation to the boiler water to effect a reduction in the boiler temperature and pressure.

A further object is to devise overheating prevention means for a hot water boiler in which the cold water supply is fed to the boiler to replace water losses therefrom under conditions effecting a tempering or" the cold water before mixiing with the main body of hot water in the boiler.

A further object is to provide an apparatus capable of separate assembly and installment as a unit on or in association with a hot water boiler for accomplishing any of the foregoing results and which is arranged to utilize the pressure created by the steam flashing of overheated water which is discharged from the boiler as a means for controlling the introduction of cold water and the interruption of the electrical circuit which includes the firing means for the boiler.

A further object is to provide an apparatus of the character indicated which includes as a portion thereof the ordinary pressure relief valve for relieving water from the boiler.

ihese and further objects of the invention will be set forth in the following specification, reference being had to the accompanying drawings, and the novel means by which said objects are effectuated will be definitely pointed out in the claims.

In the drawings:

Fig. 1 is an elevation of a typical hot water boiler showing my improved apparatus as to one form thereof operatively associated therewith.

Fig. 2 is an enlarged, sectional view of a portion of the apparatus shown in Fig. 1.

Fig. 3 is a view similar to Fig. 1, but showing the apparatus conditioned to feed tempered Water to the boiler to replace water loss.

Fig. 4 is a modified, fragmentary view of the apparatus, similar to that shown in Fig. 2, but in which the throttling discharge is embodied in the apparatus, as distinguished from the drain pipe. I

Fig. 5 is an isometric view showing a further modified arrangement for feeding tempered cold Water to the upper part of the boiler.

Fig. 6 is an enlarged, sectional elevation of the apparatus unit including a pressure reducing valve and a pressure relief valve, as shown in Fig. 5, which is conditioned to utilize the steam flashing of overheated water discharged from the boiler as a control on the admission of cold water to the boiler and as a means for interrupting the electrical circuit which includes the firing means for the boiler.

Fig. '7 is a, fragmentary section along the line l-'l in Fig. 6.

Fig. 8 is an enlarged, sectional elevation of the dip tube fitting mounted in the top of the boiler as shown in Fig. 5.

Fig. 9 is an isometric view showing the association of the apparatus illustrated in Fig. 6 with the heat exchanger indicated in Fig. 3.

This application is a continuation-in-part of 3 my copending application for Heating System, Ser. No. 59,150, filed November 9, 1948, and now abandoned.

Referring to Fig. l of the drawings, the numeral I designates a hot water boiler which may be fired in any suitable manner, automatically or manually, and which may or may not be equipped with the customary controls. A supply pipe H leads from the top of the boiler to radiators (not shown) and a return line l2 connects the radiators with the lower part of the boiler. If desired, the pipe I I may include a flow control valve and the return pipe l2 a circulating pump, all in accord with standard practice, but since these well known parts do not form any part of the invention, they have not been illustrated. However, the invention is not restricted in its application to a boiler forming part of a hot water heating system, but is capable of adaptation to hot water boilers generally,

My improved apparatus is indicated generally by the numeral 13 and it may be installed as a unit, or assembled on the job, but in either case is positioned above the boiler. It comprises a casing l4 whose lowerportion is connected at one end to the upper portion of the boiler by a fitting l5 whose internal diameter is sufiiciently large to insure a one-pipe, circulating flow between the boiler and casing so that the water within the casing is always at substantially the same temperature as the hottest boiler water during non-relieving I periods and so that any steam condensed in the casing will return to the boiler. The fitting [5 also insures that, when the water in the casing 14 is cooled as hereinafter described, this water, lower in temperature than that in the boiler, will flow through the fitting into the boiler and serve to reduce its temperature.

At the opposite end of the casing M, its upper portion is connected by a pipe is to t e inlet chamber ll (see Fig. 2 of a pressure relief valve 28 which is of standard construction in every respect except in the particulars presently noted. It comprises a housing is that is internally di vided by a wall 2a which, together with a diaphragm 2 clamped to the upper side of the housing 9 by a cover 22, defines the chamber ii. The wall 20 is provided with a relieving port 23 which is operably related to a pressure relief valve element 24 positioned in the chamber ii and carried on the lower end of a rod 25 which is secured to and extends upwardly through the diaphragm 2i and the interior of the cover 22 and outwardly of the latter. A manually operated, releasing handle 26 is pivotally secured to the part of the rod 25 which extends without the cover 22 and a helical spring 2!, encircling the rod 2 5 and interposed between a washer 28 which abuts the interior of the cover 21. and the upper surface of the diaphragm 2 i, maintains the valve element 24 in closing relation to the port 23 except when the boiler pressure operating against the diaphragm is sufficient to overcome the loading of the spring.

An outlet or draining chamber 2% is formed in the housing is; beneath the wall iii and its lower boundary is constituted by a diaphragm 3i; which is clamped to the lower side of the housing is by the upper end of an intermediate housing 33. A pipe 32 communicating with the outlet chamber 29 providesmeans for discharging water that is relieved from the boiler to a drain when the valve element 25 opens and this pipe is sized to create a back pressure in '4 the chamber 29 whenever steam is present there in under conditions presently described.

A diaphragm 33 having a smaller diameter than that of the diaphragm 38 is clamped against the lower end of the housing 3! by the upper end of a cold water housing 34. A chamber 35 is formed within the housing 31 by the diaphragms and 33 and this chamber is in constant communication with the atmosphere through apertures 35. The upper end of a rod 31 is secured to the diaphragm 30 while the lower portion of this rod extends through and is fastened to the diaphragm 33 and has secured on its lower end within the housing 34 a valve element 38 which is operably related to a cold water port 3% provided in a wall ll] that divides the housing into inlet and outlet chambers 45 and 42, respectively. The valve element 38 engages the inlet side of the port 3-9 and downward movements of this element, as hereinafter described, communicates the chamber 4| with the chamber The diaphragm 3B is biased to normally hold the valve element 38 in closing relation to the, port 39, while the diaphragm 33 is merely a convenient means for closing the upper portion of the chamber 52 and for providing a packing for the rod 31.

A supply pipe 43, communicating with a source of cold water under pressure, which may be a city main or equivalent source, has its delivery end connected to the. inlet chamber at, while the outlet chamber 42 is connected by a pipe 44 with one end of a pipe loop (if; or generally a hollow member positioned within and in heat exchanging relation to the water in the casing i l. The opposite end of the loop 45 is connected to a pipe it leading to a drain. The casing l4 and loop at constitute a heat exchanger between the cold water supply when the valve element 38 opens and the boiler water, and, in this connection, it will be understood that the loop 45 illustrates diagrammatically any arrangement, including coils, of the pipe within the casing and that the pipes =44 and 36 constitute the inlet and discharge outlets, respectively, to the loop. The essential requirement is that the pipe within the casing shall be composed of a suitable material and have a surface adequate to effect the desired heat exchange.

Under operating conditions, the boiler 10 functions in its usual manner and, if connected to a radiator system, supplies hot water thereto in the normal fashion. The pressure relief valve iii operates in the customary manner by opening of the valve element 24 to relieve water from the boiler when the boiler pressure exceeds the setting thereof, since the inlet chamber of the valve i8 is always in communication with the casing M and the pressure of the water therein is constantly equal to that of the boiler. However, the pressure in the chamber 29 is that of the atmosphere during periods when the pressure relief valve 24 is closed and advantage is taken of this situation to effect a pressure control on the operation of the valve element 38 and so regulate the flow of cold water for indirectly cooling the boiler when overheated.

So long as the temperature of the boiler water discharged into the chamber 29 is such that it does not flash into steam when exposed to the atmospheric pressure in this chamber, the diaphragm 30 is unaffected and the relieved water is evacuated through the drain pipe 32. However, if the pressure relief valve element 24 opens when the temperature of the boiler Water is such that the water flowing into the chamber 29 wholly or partially flashes into steam at the ma terially reduced pressure in this chamber, a pressure condition is created which acts against and deflects the diaphragm 30 downwardly and opens the valve element 38. This action is facilitated by the throttling control on the discharge of the steam exercised by the pipe 32 which is sized for this purpose in conjunction with a relatively larger sizing of the port 23 and which serves to retain pressure in the chamber 29 for a time sufficient to secure practical results from the opening of the valve 38. For example, in one unit that proved successful, the effective diameter of the diaphragm was four inches, the inside diameter of the pipe 32 was three-fourths of an inch, and the diameter of the port 23 was one inch.

Cold water then fiows through the pipe loop 45, abstracts heat from the hot boiler water and discharges this heat to a drain through the pipe 45. The cold water fiow continues as long as there is adequate pressure effective against the diaphragm, condensing any steam that may be present in the casing 14 and dissipating the excess heat so that the boiler pressure drops, the pressure relief valve element 24 closes and the diaphragm 30 returns to a position closing the valve element 38 and interrupting the cold Water how. The two-way fiow characteristics of the fitting l5 insures that the cooled water in the casing l4, whose temperature is then lower than that of the water in the boiler, will flow into the boiler to cool the same. During this operation, the pressure relief valve element 24 is characterized by a piloting relation to the cold water supply valve 38. The closing of the latter valve is assisted by the cold Water pressure acting thereagainst.

The apparatus shown in Fig. 1 is capable of attachment to old or new boilers and an obvious modification may consist in immersing the pipe loop 45 within the boiler, thu eliminating the casing l4. In this event, the pressure relief valve l8 would be connected by its pipe I6 directly to the boiler and the remainder of the apparatus would be the same as that described.

This arrangement for preventing overheating in hot water boilers is therefore wholly independent of the type of firing employed for the boiler and is also independent of any failure of the electrical circuits which are commonly associated with automatically fired boilers. Regardless of whether or not the boiler is continuously fired, my improved arrangement operates automatically to reduce the temperature of the Water in the boiler to any predetermined point.

The modification illustrated in Fig. 3 is identical with that shown in Fig. 1 with the exception that the drain pipe 46 is replaced by a pipe 4? connecting the loop 45 with the lower part of the boiler. Otherwise, like parts in the two figures are designated by like numerals.

With this arrangement, it will be obvious that when the valve 35; opens and assuming a higher pressure of the water supply than the then pressure in the boiler, the cold water will flow through the loop 45 to thereby reduce the temperature of the boiler water as above described and at the sametime raise its own temperature. This tempered cold water then flows into the boiler, thus providing a means for automatically preventing a dangerous lowering of the water line in the boiler.

In Fig. 4 is illustrated a variation of that portion of the apparatus which is shown in Fig. 2, the modification consisting in locating within the apparatus the throttling control for the steam discharged from the chamber 29 instead of sizing the drain pipe 32 for this purpose. Like parts in Fig. 4 are designated by the same numerals as in Fig. 2.

The inlet end of a drain pipe 48 is mounted in a hollow extension 49 forming part of the housing l9 and communication between this inlet end and the chamber 29 is through a throttle orifice 55 provided in a wall 5| which is bridged across the interior of the extension 49. The orifice 5B fulfils the same throttling function with, respect to the discharge of steam from the chamber 29 as does the drain pipe 32 in Fig. 2 and hence would have a diameter equal to the internal diameter of this pipe when used with thediaphragm 30. The drain pipe 48 does not exercise any throttling control.

In Figs. 5 to 8, inclusive, are illustrated a further modification, particularly of that shown in. Fig. 3, and wherein the pressure engendered by the steam flashing of overheated water also con trols the introduction of cold water into the boiler with provision for pre-tempering thereof and, in. addition, interrupts the electrical circuit to the firing unit for the boiler, whether stoker, gas oroil fired, so that the heat input is out off.

Referring specifically to Fig. 5 which diagram-- matically shows the systemic relation of the sev-- eral parts, the numeral 52 designates a hot water boiler having mounted in the upper wall thereof a fitting generally indicated by the numeral 53 which is more particularly disclosed and claimed in U. S. Letters Patent No. 2,500,621, dated March l l, 1950, and is illustrated in Fig. 8. Specifically, this fitting includes a nipple 54 whose opposite ends are respectively threaded in the top wall of the boiler 52 and the lower coaxial branch 55 of a T This T also includes a lateral branch 5'! which connects by a pipe 58 with an expansion tank 59 and a wall 60 which is bridged internally of the T 55 slightly above the connection of the pipe 58 thereto. The upper end of a dip tube Ell extends through and is rested on the wall 5% and the remainder of the tube extends downwardly in coaxial and spaced relation to the T 56 and nipple 54 and well below the top of the boiler, i. e., in a region where the water in the boiler is substantially free of air bubbles which may pass freely upward through the annular space between the nipple 54 and tube El and thence to the expansion tank 59.

Substantially bubble free, boiler water flows upwardly through the tube 5| into the lower end of a pipe 52 which is threaded in the upper coaxial branch 53 of the T 55. The opposite end of the pipe 52 (see Fig. 5) connects with the inlet of a fiow control valve 64 of that well known type wherein the valving element is gravity moved to closure and opened by a circulating pressure in the system. The valve 54 discharges to a supply pipe 55 leading to a plurality of radiating devices (not shown) and from these devices a return pipe 55 including a circulating pump 67 connects with the bottom of the boiler. Operation of the pump 57 may be controlled in the usual manner by a thermostat responsive to the radiating devices.

From the upper part of the boiler 52 also extends a pipe 59 whose delivery end connects with an apparatus unit 69 composed of a pressure relief valve 10 and a pressure reducing valve 'H modified as presently described, The discharge accept-6.:

from 'thereliei valve 19 is evacuated to a drain through a pipe 12 and a cold water supply pipe it connects with the inlet side of the reducin valve ll while the discharge side thereof connests through a pipe 14 which preferably includes a check valve 1'5 with the pipe 53 and hence with the boiler. The valve 15 is conditioned to permit flow only from the reducing valve H tothe boiler and closes by gravity.

The electrical circuit for the system shown in Fig. includes a main controlswitch 18, connected to a suitable power source, and from this switch leads a hot wire T! which connects in series a switch, presently described and located in the apparatus unit 69, a high limit, immersion control it of characteristic type mounted in the upper part of the boiler'52, anda firin unit 19 which connects by aground wire 80 with the main switch it.

Referring to Fig. 6, the apparatus unit 69 includes an elongated casing 8! that is common to the relief and reducing valves 19 and H. The left end of the casing 3|, as viewed in Fig. 6, is

vinteriorly divided by a wall 82 to provide a chamber cs that communicates with the delivery end of the pipe- 68 leadingfrom the boiler and also with a chamber 86. The wall 82 includes a horizontal portion that is apertured to receive a valve disk 8? is secured to the underside of this diaphragm. The valve disk 8'! is normally maintained in closing contact with the seat 86 by a spring 98 whose opposite ends respectively abut a spring plate 9] which seats against the upper central portion of the diaphragm M and a spring plate 92 that abuts an adjusting nut W carried by a frustoconical cover 93 whose lower, annular end is outwardly flanged to clamp the periphery of the diaphragm 89 against the wall 88.

While the pressure relief valve "it may be of the standard type, it is preferably, and as illustrated, arranged according to the valve disclosed and claimed in the application of Henry P. Birkemeier, Ser. No. 650,649, filed February 27, 1946, now Patent 2,603,231. Briefly, the diaphragm 3% is conditioned to flex upwardly at the etting of the valve, normally 30 p. s. i., without raising the valve disk 8'! until the boiler pressure rises slightly above the valve setting. During this operation, the washer SI slides along the nut 95 which clamps the central portion of the diaphragm 38 against the valve disk 81 until this Washer engages a shoulder 95 on the nut t4, whereupon the valve disk 87 moves upward with a snap action toprovide a. substantial relief through the bushing 85. .A valve of this type eliminates a dribble relief which is characteristic of standard forms of relief valves.

'With respect to the pressure reducing valve l i, the wall 88 includes a second opening that is bridged by a diaphragm 96 whose periphery is clamped against the wall by the lower, outwardly flanged end of a frustoconical casing ti. Accord. ingly, the diaphragm 9B is responsive to pressure 1 in the chamber 84 under conditions presently described. The upper, inwardly flanged endyoi the casing 97 clamps the periphery of a second diaphragm 98, smaller in diameter than and spaced from the diaphragm 96, against the lower side of a fitti-ng "99 which includes an opening bridged by-the diaphragm 98. The lateral wall 8. ofthc. casin 93! ay i lud one or m e om tures 169 to insure free movement of the diaphragm pfifi and 98.

The fitting 9.3 (se Fi s- 6 and 7) s i ter a divided by a wa l 191 to form a nl am Hi2, which ommun ca w t delivery ndor the cold water s pp pipe 3. a n o t chamher H33, partially defined by the diaphragm 98,, which communicates with the inlet end of the pipe 14 leading to the boiler.

A horiz nta po ion of h w l i is a tured in coaxial relation to the diaphragms 96 and 93 to, threadingly receive a bushing I04 whose upp r n er e s a valve eat that is engaged by a valve I05. This valve is carried on the upper end of a stern I06 that extends down-.- wardly through and in substantial clearance relation tothe bore oi the bushing I04 and is con tinued successively through the diaphragm 9B and a plate ill! abutting the underside thereof for threaded connection with a spacer W8 interposed between the plate ill? and a washer Hi9 resting on the top side of the diaphragm 96. Abutting the underside of the diaphragm 96 is a plate I I0 and a screw Hi extends upwardly through the plate Mt. diaph a m t5. w s m9 t upper end is threaded in the spacer its.

th fo o n it w be appare that the diaphragms 95 and as are locked together for simultaneous movement, that when pressure beneath the diaphragm 96 is controlling, the valve Hi5 will be raised to an open position to admit cold water, and that when pressure above the diaphragm 98 is controlling, the valve "35 is moved to the closed position shown in Fig. 6. An initial and constant bias acting in a direction tending to open the valve W5 is provided by a spring iii interposed between the plate lid and a plate H3 which rests on the upper end of an adjustingscrew i it that is threaded throughand extends below the casing wall 8!.

For the purpose or" interrupting the power circuit to the firing unit 15 when the boiler becomes overheated, the. casing end wall H5 includes a port lit that is bridged by a diaphragm I ll outwardly of the wall H5. IChe diaphragm HT car.- ries a finger lid that is located adjacent a switch .(schematically shown) forming part of the hot here??? i ihen'surficient pressure is created in the chamber til as presently described, the outward flexing of the diaphragm lli moves the switch M5 to the dotted .or open position shown, thus cutting out the firing unit l9. After the necessary repairs have :been effected, the power to the firing unit is reestablished by movn g the .pushhutton its to restore the switch i :9.

In describing the operation of the system shown 'iaig. 5, it will :be assumed that the system is empty and therefore lacking in pressure, that the spring Si; has'heen adjusted by the nut 92 to a setting of 30' s. i. so that the valve disk 8'! is o-lcsed, that the spring H2 has been adjusted to keep the cold water valve M5 open below a syspressu-rexof 12 p. s. i., that the switch H9 i open, and that cold water pressure available in thepipe't'd 'is of the order of 35 p. s. i. or greater as is common in many localities, particula'rly-ur han districts.

new a cool; (not shown) in the pipe '73 is opened, cold water .will'flow successively through the chamber W2, here of the bushing HM, chamoer E- ii'd, pipe it, the check valve 35 being opened by the cold water pressure, the pipe 58 and the nipple to the boiler 52 and thence in the usual manner through the supply and return pipes 65 and 66, respectively, to the radiating devices, thus filling the system. Water will also also rise through the pipe 58 in to the expansion tank 59 and trap air therein. With the system filled, pressure is equalized on opposite sides of the check valve 15 which closes by gravity. If the relief valve I was opened during filling of the system, it will close when the system pressure drops to 30 p. s. i. or slightly below. Further, the pressure trapped in the chamber I03 being greater than the biasing pressure set up by the spring 2, the former pressure will flex the diaphragm 98 to move the cold water valve I05 to the closed posiiton shown in 6. The system is now ready for operation which can be effected by closing the switch 5 i to thus start the firing unit I9.

During normal operation, the valve disk 81 may open from time to time to discharge water to the chamber 84 for evacuation through a port I2I in the lower casing wall BI and thence to the drain pipe 12. The chamber 84 is always at atmospheric pressure and the water discharged thereto does not change state so that pressure is not exerted against the diaphragm 95. Further, and also during normal operation, the pressure reducing valve 1| will open in the customary manner to feed cold water to the system whenever the ressure therein is low enough and the system can receive water.

Generally speaking and in the actual arrangement shown in Fig. 5, the so-called normal operation is related to the continued functioning of the immersion control 18 whose contacts automatically open whenever the boiler water temperature rises to the point desired to thereby break the firing unit circuit and automatically close below the set temperature to again start the firing unit 19. If, for any reason, the contacts of the control 18 fall to open, heat input to the boiler will continue and the temperature of the boiler water will rise very rapidly. This condition will be aggravated if the pump 61 is then out of operation because of the confinement of the boiler water due to the closed fiow control valve 64.

When the pressure rises above that for which the relief valve 70 is adjusted, the latter opens and if the temperature of the discharged boiler water is sufiiciently high, this water flashes into steam in the chamber 84 at the substantially reduced pressure existing therein. The increased pressure thus created in the chamber 84 acts against the diaphragm 96, which is larger than the diaphragm 98, to thereby open the cold water valve I05.

To secure practical results from the foregoing operation, it is necessary that the chamber pressure be initially adequate for the purpose and that it be maintained above a minimum point for a time sufficient to obtain practical results from the opening of the valve I05. As in the other modifications, this result is attained by exercising a throttling control on the discharge of steam from the chamber 84. By way of example and as illustrating a successfully operated unit, the diameter of the port I2I was three-eighths of an inch, the effective diameter of the diaphragm 96 was about four and one-half inches, and the discharging capacity of the relief valve In at about 33 p. s. i. was approximately eight gallons per minute.

Under the conditions stated, an initial pressure of about 6 p. s. i. was obtained in the chamber 84 which tapered down to about 43/ p. s. i. due to constant discharge through the port I2ll. Within this pressure range, the apparatus unit 69 was operative to secure a flow of cold water to the boiler.

It will be understood that different installations may require relief valves having other discharge capacities. These variations may require discharge ports having different diameters within the general rule that each such port shall be sized in relation to the discharge capacity or" the associated relief valve that the desired throttling control is obtained on the discharge of steam from the chamber 84.

A further feature of the invention is the utilization of the steam pressure in the chamber 84 as a means of interrupting the electrical circuit including the firing unit 19. Under the condi tions noted, this pressure actuates the diaphragm iii to thereby swing the switch II9 to the open or dotted position shown in Fig. 6. Since this arrangement positively stops the operation of the system, it serves as a signal that the system needs repair and, after the latter has been effected, operation ma be resumed by actuating the push button H9 to restore the switch H9.

It will be understood, however, that the apparatus unit 69 has utility, in the absence of the diaphragm actuated switch I19, to supply cold water to an overheated boiler to prevent excessive loss of Water therefrom and possible exposure of the crown sheet. When so used, the unit 69 is wholly independent of the type of firing unit as well as of the failure of the electrical circuits commonly employed with automatically fired boilers.

An additional feature of the system shown in Fig. 5 is the ability to temper the entering cold water before it reaches the boiler and, in this connection, this system is a modification of that illustrated in Fig. 3. From Figs. 5 and 8, it will be apparent that the dip tube BI is constantly filled with water substantially at boiler temperature. Since in the average, domestic size boiler, this tube has a length of about twelve inches, a substantial tempering of the entering cold water is obtained as it flows along the exterior of this tube.

In Fig. 9 is illustrated a further modification in which the apparatus unit shown in Figs. 5 and 6 is employed in the arrangement shown in Fig. 3 as a substitute for the apparatus unit illustrated in the latter figure. Like parts in all of these figures are indicated by like numerals.

The heat exchanger casing I4 connects by a pipe I22 with the inlet to the pressure relief valve I0 and water or steam discharged thereby is evacuated through the throttling port III to the drain pipe I2. Cold water passing through the pressure reducing valve II flows through a pipe I23 to the inlet end of the coil 45 and the outlet end of this coil connects by a pipe I24 with the lower part of the boiler I0. The apparatus unit 69 functions to control the admission of cold water in the same manner as in Fig. 5, while the coil 45, being bathed by boiler temperature water, tempers the incoming cold water before delivery to the boiler.

I claim:

1. Apparatus for preventing overheating of a hot water boiler comprising a hollow member adapted for immersion in and in heat exchanging relation to boiler temperature water and having a discharge outlet and an inlet for connection to a cold water supply, a normally closed valve for controlling flow of cold water through the member, a draining chamber open to the atmosphere, means responsive to boiler pressure for discharging boiler water to the chamber, means for opening the valve responsive to a discharge of boiler water to the chamber having a temperature sufiiciently high to fiash into steam at atmospheric pressure, and means for throttling the discharge of steam from the chamber.

2. Apparatus for preventing the overheating of a hot water boiler comprising a casin adapted for connection to the upper part of the boiler to contain water substantially at boiler temperature, a hollow member located in heat exchanging relation tothe water in the casing and having a discharge outlet and an inlet for connection to a cold water supply, a normally closed valve for controlling iiow of cold water through the member, a draining chamber open to the atmosphere, means responsive to boiler pressure for discharging boiler water to the chamber, means for opening the valve responsive to a discharge of boiler water to the chamber having a temperature sufficiently high to flash into steam at atmospheric pressure, and means for throttling the discharge of steam from the chamber.

3. Apparatus for preventing overheating of a hot water boiler comprising a first valve operable at a predetermined boiler pressure to discharge hot water from the boiler, a draining chamber open to the atmosphere for receiving the discharge from the first valve, a hollow member adapted for immersion in and in heat exchanging relation to boiler temperature water and having a discharge outlet and an inlet connected to a cold water supply, a normally closed valve operably related to the discharge side of the first valve and opening to permit flow of cold water through the member when the first valve discharges to the chamber boiler water having a temperature high enough to flash into steam at atmospheric pressure, and means for throttling the discharge of steam from the chamber.

4. Apparatus for preventing overheating of a hot water boiler comprising a first valve operable at a predetermined boiler pressure to discharge hot water from the boiler, a draining chamber open to the atmosphere for receiving the discharge from the first valve, a. hollow member adapted for immersion in and in heat exchanging relation to boiler temperature water and having a discharge outlet and an inlet connected to a cold water supply, a normally closed valve for controlling the flow ofv cold water having a part exposed in the chamber to the discharge side of the first valve and pressure oper ated in an opening direction by the first valve discharge to the chamber of boiler water having a temperature high enough to. flash into steam at atmospheric pressure, and, means for throttling the discharge of steam from the chamber.

5. Apparatus for preventing overheating of a hot water boiler comprising first and second valves pressure. operated inv an opening direction for respectively controlling the discharge of hot water from the boiler and a cold water supply, the first valve being responsive toboiler pressure, a draining chamber open to the atmosphere for receiving the discharge from the first valve, a hollow member adapted. for immersion in and in heat exchanging relation to boiler temperature water and having a discharge outlet and an inlet connected to the discharge side of the second valve, the second valve being operably related to the discharge side of the first valve and opening to permit flow through the memb r when sive to a predetermined boiler 12 the firstvalve discharges to the chamber boiler Water having a temperature. high enough to fiash into steam at atmospheric pressure, and means for throttling the discharge of steam from the chamber.

6. Apparatus for preventing overheating of a hot water boiler comprising first and second, normally closed valves for respectively controlling the discharge of hot water from the boiler and a cold water supply, the first valve opening in response to a predetermined boiler pressure, a draining chamber open to the atmosphere for receiving the discharge from the first valve, a hollow member adapted for immersion in and in heat exchanging relation to boiler temperature water and having a discharge outlet and an inlet connected to the discharge side of the second valve, the second valve having a part exposed in the chamber to the discharge side of the first valve and pressure operated in an opening direction when the first valve discharges to the chamber boiler water having a temperature high enough to flash into steam at atmospheric pressure, and means for throttling the discharge of steam from the chamber.

7. Apparatus for preventing overheating of a hot water boiler comprising a first valve responsive to a predetermined boiler pressure for evacuating hot water from the boiler and having a draining chamber open to the atmosphere and provided with a movable wall, a hollow member adapted for immersion in and in heat exchanging relation to boiler temperature water and having a discharge outlet and an inlet for connection to a cold water supply, a valve connected to the movable wall for controlling the how of cold water and opened by the pressure effective against the wall when the first valve discharges to the chamber boiler water having a temperature high enough to flash into steam at atmospheric pressure, and means for throttling the discharge of steam from the chamber.

8. Apparatus for preventing overheating of a hot water boiler comprising a first valve responpressure for evacuating hot Water from the boiler and having a draining chamber open to the atmosphere and partially defined by a diaphragm secured at its periphery to the walls of the chamber, a hollow member adapted for immersion in and in heat exchanging relation to boiler temperature water and having a discharge outlet and an inlet for connection to a cold water supply, a valve connected to the diaphragm for controlling the fiow of cold water and opened by the pressure effective against the diaphragm when the first valve discharges to the chamber boiler water having a temperature high enough to flash into steam at atmospheric pressure, and means for throttling the discharge of steam from the chamber.

9. The combination of a boiler, and means for preventing overheating of the boiler comprising a hollow member immersed in and in heat exchanging relation to boiler temperature water and having a discharge outlet and an inlet for connection to a cold water supply, a normally closed valve for controlling fiow of cold water through the member, a draining chamber open to the atmosphere, means responsive to boiler pressure for discharging boiler water to the chamber, pressure actuated means for opening the valve responsive to a discharge of boiler water to the chamber having a temperature high enough to flash into Steam at atmospheric pres- 13 sure, and means for throttling the discharge of steam from the chamber.

10. The combination of a boiler, and means for preventing overheating of the boiler comprising a casing circulatingly connected to the upper part of the boiler to contain water substantially at boiler temperature, a hollow member located in heat exchanging relation to the Water in the casing and having a discharge outlet and an inlet for connection to a cold water supply, a normally closed valve for controlling flow of cold water through the member, a draining chamber open to the atmosphere, means responsive to boiler pressure for discharging boiler water to the chamber, pressure actuated means for opening the valve responsive to a discharge of boiler water to the chamber having a temperature high enough to flash into steam at atmospheric pressure, and means for throttling the discharge of steam from the chamber.

11. The combination of a boiler, and means for preventing overheating of the boiler comprising a first valve operable at a predetermined boiler pressure to discharge hot water from the boiler, a draining chamber open to the atmosphere for receiving the discharge from the first valve, a hollow member immersed in and in heat exchanging relation to boiler temperature water and having a discharge outlet and an inlet for, connection to a cold water supply, a normally closed valve operably related to the discharge side of the first valve and pressure actuated in an opening direction to permit flow of cold water through the member when the first valve discharges to the chamber boiler water having a temperature high enough to flash into steam at atmospheric pressure, and means for throttling the discharge of steam from the chamber.

12. The combination of a boiler, and means for preventing overheating of the boiler comprising first and second valves pressure operated in an opening direction for respectively controlling the discharge of hot water from the boiler and a cold water supply, the first valve being responsive to boiler pressure, a draining chamber open to the atmosphere for receiving the discharge from the first valve, a hollow member immersed in and in heat exchanging relation to boiler temperature water and having a discharge outlet and an inlet connected to the dis- I charge side of the second valve, the second valve being operably related to the discharge side of the first valve and pressure actuated in an opening direction to permit flow through the member when the first valve discharges to the chamber boiler water having a temperature high enough to flash into steam at atmospheric pressure, and means for throttling the discharge of steam from the chamber.

13. Apparatus for preventing overheating and lowering the water line of a hot water boiler comprising a hollow member adapted for immersion in and in heat exchanging relation to boiler temperature water and having a discharge outlet and an inlet for connection to a cold water supply, a pipe for connecting the outlet to the lower part of the boiler, a normally closed valve for controlling flow of cold water through the member, a draining chamber open to the atmosphere, means responsive to boiler pressure for discharging boiler water to the chamber, pressure actuated means for opening the valve responsive to a discharge of boiler water to the chamber having a temperature sufliciently high to flash into steam at atmospheric pressure, and means for 7 14 throttling the discharge of steam from the chamber.

14. The combination of a hot water boiler, and means for preventing overheating and lowering the water line in the boiler comprising a hollow member immersed in and in heat exchanging relation to boiler temperature water and having a discharge outlet and an inlet for connection to a cold water supply, a pipe connecting the outlet to the lower part of the boiler, a normally closed valve for controlling flow of cold water through the member, a draining chamber open to the atmosphere, means responsive to boiler pressure for discharging boiler water to the chamber, pressure actuated means for opening the valve responsive to a discharge of boiler water to the chamber having a temperature sufficiently high to flash into steam at atmospheric pressure, and means for throttling the discharge of steam from the chamber.

15. Apparatus for preventing lowering of the water line of a hot water boiler comprising a normally closed valve for controlling a cold water supply to the boiler, a chamber having port means draining to the atmosphere, means responsive to boiler pressure for discharging boiler water to the chamber, and means for opening the valve responsive to a discharge of boiler water to the chamber having a temperature suificiently high to flash into steam at atmospheric pressure, the port means constituting the sole terminal outlet for all discharge from the boiler and being sized to throttle the discharge of steam from the chamber.

16. Apparatus for preventin lowering of the water line of a hot water boiler comprising first and second valves pressure operated in an opening direction for respectively controlling the discharge of hot water from the boiler and a cold water supply to the boiler, the first valve being responsive to boiler pressure, a chamber having port means draining to the atmosphere for receiving the discharge from the first valve, the second valve being operably related to the discharge side of the first valve and opening to permit cold Water flow to the boiler when the first valve discharges to the chamber boiler water having a temperature high enough to flash into steam at atmospheric pressure, and the port means constituting the sole discharge outlet from the boiler to the atmosphere and being sized to throttle the discharge of steam from the chamber.

17. Apparatus for preventing lowering of the water line of a hot water boiler comprising first and second valves pressure operated in :an opening direction for respectively controlling the discharge of hot water from the boiler and a cold water supply to the boiler, the first valve being responsive to boiler pressure, a chamber having port means draining to the atmosphere and constituting the sole outlet for any discharge from the boiler, a diaphragm forming part of the wall of the chamber and connected to the second valve, the diaphragm being responsive to pressure in the chamber and acting to open the second valve to permit cold water flow to the boiler when the first valve discharges to the chamber boiler water having a temperature high enough to flash into steam at atmospheric pressure, and the port means being sized to throttle the discharge of steam from the chamber.

18. The combination of a hot water boiler, a normally closed valve for controlling a cold water supply to the boiler, a chamber having port means draining to the atmosphere, means responsive to" boiler press-ureter discharging boiler water to the chamber, means for opening the valve responsive to a discharge of boiler water to the chamber hav ng a temperature sufficiently high to flash into steam at atmospheric pressure, the port means constituting the sole terminal outlet for all discharge from the boiler and being sized to throttle the discharge of steam from the chamber, and means for tempering the coldvv'ater before delivery to the boiler by flowing the same into heat exchange relation to boiler temperature water.

19. The combination or a hot Water boiler, a fitting mounted inthe top Wall of the boiler in cluding a dip tube having one end extending substantially below the top Wall with its opposite end connected to a supply pipe leading to radiating devices, the dip tube being constantly filled with water substantially at' boiler temperature, a normally closed valve for controlling a cold Water su ply, passage means connecting the outlet of the valve With the boiler, a part of the passage means surrounding the dip tube whereby cold water flowing to the boiler is tempered by heat exchange with the Water in the dip tube, a chamber having port means draining to the atmosphere, means responsive to boiler pressure for discharging boiler water to the chamher, and means for opening the valve responsive to a discharge of boiler water to the chamber having a temperature sufiiciently high to flash into steam at atmospheric pressure, the port means constituting the sole terminal outlet for 16 all discharge from the boiler and being sized to throttle the discharge of' steam from the chamber;

20. The combination or a hot Water boiler, a firing unit for the boiler, a normally closed valve for controlling a cold water supply to the boiler, a chamber having port means draining to the atmosphere, means responsive to boiler pressure for discharging boiler Water to the chamber, means for opening the valve responsive to a discharge of boiler water to the chamber having a temperature sufiiciently high to flash into steam at atmospheric pressure, the port means constituting the sole terminal outlet for all discharge from the boiler and being sized to throttle the discharge of steam from the chamber, and an electrical circuit including the firing unit and switch means responsive to said steam flashing pressure for interrupting the operation of the firing unit.

EDWIN B. TID-D.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 973,603 Winslow Got. 25, 1910 1,916,426 Hughes et a1 July {15, 1933 2,176,539 Moore Oct. 17, 1939 2,190,382 Moore Feb. 13, 1940 2,326,559 Proctor Aug. 10, 19%3 2,335,785 Moore Nov. 30, 1943 

